Redolog and binlog

mysql The log system of

• mysql There are two important logs in

• redolog

• innodb The engine provides

• Logic log , Record operations on data , must id=2 This line +1

• redolog What problem does the log solve ?

• We all write to disk frequently Efficiency is very low , therefore mysql This problem is solved by logging at design time

• mysql When updating a table , Will record one first redo log journal ,innodb Wait for idle time to write to the disk , This operation is also known as WAL(write-Ahead-Loggin)

• redolog It's fixed size , Write from the beginning , Write at the end and go back to the beginning

• redolog Then record the log of the unwashed disk

• With redo log,InnoDB It can guarantee that even if the database is restarted abnormally , No records submitted before will be lost , This ability is called crash-safe.

• binlog

• binlog from mysql server Provide

• The physical log records the changes made on the data page binlog The previous log will not be overwritten

• You may ask Why? binlog I won't support it crash-safe ?

• I said before. binlog Full log of records , Record all operations redolog Recorded operation without disc brushing

• When the database goes down and recovers binlog There is no way to know where the database went down Unable to recover precisely

• and redolog You only need to swipe the disk to recover the data

• Two-phase commit

• Guarantee binlog and redolog All written into